1. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 The Future of RF Microelectromechanical Systems (MEMS) Clark T.-C. Nguyen Dept. of Electrical Engineering & Computer Sciences University of California Berkeley, California 94720 E-mail: ctnguyen@eecs.berkeley.edu BEARS’07 Feb.15, 2007

2. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Outline Motivation: Miniaturization of Transceivers  need for high-Q Micromechanical Resonators  clamped-clamped beams  micromechanical disks Micromechanical Circuits  micromechanical filters  arraying techniques Towards RF Channel-Selection Conclusions

3. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Wireless Phone Motivation: Miniaturization of RF Front-Ends 26-MHz Xstal Oscillator Diplexer 925-960MHz RF SAW Filter 1805-1880MHz RF SAW Filter 897.5  17.5MHz RF SAW Filter RF Power Amplifier Dual-Band Zero-IF Transistor Chip 3420-3840MHz VCO Problem: high-Q passives pose a bottleneck against miniaturization 90 o 0o0o A/D RF PLL Diplexer From TX RF BPF Mixer I Mixer Q LPF RXRF LO Xstal Osc I Q AGC LNA Antenna

4. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Multi-Band Wireless Handsets Duplexer 90 o 0o0o A/D RXRF Channel Select PLL I Q LPF RXRF LO I Q AGC LNA Duplexer RF BPF LNA From TX LNA RF BPF WCDMA CDMA-2000 DCS 1800 PCS 1900 LNA RF BPF Duplexer LNA RF BPF GSM 900 CDMA From TX 90 o 0o0o I Q Tank ÷ (N+1)/N Xstal Osc Antenna The number of off-chip high-Q passives increases dramatically Need: on-chip high-Q passives

5. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 All High-Q Passives on a Single Chip WCDMA RF Filters (2110-2170 MHz) CDMA-2000 RF Filters (1850-1990 MHz) DCS 1800 RF Filter (1805-1880 MHz) PCS 1900 RF Filter (1930-1990 MHz) GSM 900 RF Filter (935-960 MHz) CDMA RF Filters (869-894 MHz) 0.25 mm 0.5 mm Low Freq. Reference Oscillator Ultra-High Q Tank Optional RF Oscillator Ultra-High Q Tanks Vibrating Resonator 62-MHz, Q~161,000 Vibrating Resonator 62-MHz, Q~161,000 Vibrating Resonator 1.5-GHz, Q~12,000 Vibrating Resonator 1.5-GHz, Q~12,000

6. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Thin-Film Bulk Acoustic Resonator (FBAR) Piezoelectric membrane sandwiched by metal electrodes  extensional mode vibration: 1.8 to 7 GHz, Q ~500-1,500  dimensions on the order of 200  m for 1.6 GHz  link individual FBAR’s together in ladders to make filters Agilent FBAR Limitations:  Q ~ 500-1,500, TC f ~ 18-35 ppm/ o C  difficult to achieve several different freqs. on a single-chip h freq ~ thickness

7. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Vibrating RF MEMS

8. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Basic Concept: Scaling Guitar Strings Guitar String Guitar Vibrating “A” String (110 Hz) Vibrating “A” String (110 Hz) High Q 110 Hz Freq. Vib. Amplitude Low Q Freq. Equation: Freq. Stiffness Mass f o =8.5MHz Q vac =8,000 Q air ~50  Mechanical Resonator Performance: L r =40.8  m m r ~ 10 -13 kg W r =8  m, h r =2  m d=1000Å, V P =5V Press.=70mTorr [Bannon et al JSSC’00]

9. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Fabrication steps compatible with planar IC processing Surface Micromachining

10. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Completely monolithic, low phase noise, high-Q oscillator (effectively, an integrated crystal oscillator) To allow the use of >600 o C processing temperatures, tungsten (instead of aluminum) is used for metallization Oscilloscope Output Waveform Single-Chip MEMS-Transistor Integration [Nguyen, Howe 1993] [Nguyen, Howe JSSC’99]

11. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Basic Concept: Scaling Guitar Strings Guitar String Guitar Vibrating “A” String (110 Hz) Vibrating “A” String (110 Hz) High Q 110 Hz Freq. Vib. Amplitude Low Q Freq. Equation: Freq. Stiffness Mass f o =8.5MHz Q vac =8,000 Q air ~50  Mechanical Resonator Performance: L r =40.8  m m r ~ 10 -13 kg W r =8  m, h r =2  m d=1000Å, V P =5V Press.=70mTorr [Bannon et al JSSC’00]

12. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Radial-Contour Mode Disk Resonator VPVP vivi Input Electrode Output Electrode ioio   Q ~10,000 Disk Supporting Stem Smaller mass  higher freq. range and lower series R x (e.g., m r = 10 -13 kg) Young’s Modulus Density Mass Stiffness Frequency: R VPVP C(t) Note: If V P = 0V  device off

13. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 1.51-GHz, Q=11,555 Nanocrystalline Diamond Disk  Mechanical Resonator Impedance-mismatched stem for reduced anchor dissipation Operated in the 2 nd radial-contour mode Q ~11,555 (vacuum); Q ~10,100 (air) Below: 20  m diameter disk Polysilicon Electrode R Polysilicon Stem (Impedance Mismatched to Diamond Disk) Ground Plane CVD Diamond  Mechanical Disk Resonator Frequency [MHz] Mixed Amplitude [dB] Design/Performance: R=10  m, t=2.2  m, d=800Å, V P =7V f o =1.51 GHz (2 nd mode), Q=11,555 f o = 1.51 GHz Q = 11,555 (vac) Q = 10,100 (air) [Wang, Butler, Nguyen MEMS’04] Q = 10,100 (air)

14. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Commercialization of MEMS Timekeepers High-Q, low drift, make possible a very stable, low power timekeeper $3.5 Billion Market ‘s pure silicon high-Q vibrating  mechanical resonator oscillator Discera TCMO  Smaller size  Lower cost  Lower power consumption  Smaller size  Lower cost  Lower power consumption Package Cap ASIC  Mechanical Resonator Die

15. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Output Custom IC fabricated via TSMC 0.35  m process Input GSM-Compliant Oscillator [Y.-W. Lin, Nguyen, IEDM’05] Offset Frequency [Hz] Phase Noise [dBc/Hz] 9-Wine-Glass Disk Array Q = 118,900 Q = 118,900, R x = 2.56 k  9-Wine-Glass Disk Array Q = 118,900 Q = 118,900, R x = 2.56 k  9-WG Disk Array @ 62 MHz Single WG Disk @ 62 MHz Down to 13 MHz GSM spec Satisfies Global System for Mobile Communications (GSM) phase noise specifications! All made possible by mechanical circuit design!

16. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Integrated Micromechanical Circuits

17. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Micromechanical Filter Design Basics RQRQ vovo vivi RQRQ VPVP  xoxo vivi oo  xoxo vivi oo  vovo vivi oo  vovo vivi oo Disk Resonator Coupling Beam Bridging Beam Termination Resistor Loss Pole

18. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Frequency [MHz] Transmission [dB] P in =-20dBm In Out VPVP Sharper roll-off Loss Pole Performance: f o =9MHz, BW=20kHz, PBW=0.2% I.L.=2.79dB, Stop. Rej.=51dB 20dB S.F.=1.95, 40dB S.F.=6.45 Performance: f o =9MHz, BW=20kHz, PBW=0.2% I.L.=2.79dB, Stop. Rej.=51dB 20dB S.F.=1.95, 40dB S.F.=6.45 Design: L r =40  m W r =6.5  m h r =2  m L c =3.5  m L b =1.6  m V P =10.47V P=-5dBm R Qi =R Qo =12k  [S.-S. Li, Nguyen, FCS’05] 3CC 3 /4 Bridged  Mechanical Filter [Li, et al., UFFCS’04]

19. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Micromechanical Filter Circuit 1/k r mrmr crcr mrmr crcr mrmr crcr -1/k s 1/k s -1/k s 1/k s 1/k b -1/k b CoCo CoCo 1:  e  e :1 1:  c  c :1 1:  b  b :1 /4  /4 Input Output vivi RQRQ RQRQ vovo VPVP Bridging Beam Coupling Beam Resonator  vovo vivi

20. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Micromechanical Filter Circuit 1/k r mrmr crcr mrmr crcr mrmr crcr -1/k s 1/k s -1/k s 1/k s 1/k b -1/k b CoCo CoCo 1:  e  e :1 1:  c  c :1 1:  b  b :1 /4  /4 Input Output vivi RQRQ RQRQ vovo VPVP Bridging Beam Coupling Beam Resonator  vovo vivi

21. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Micromechanical Filter Circuit 1/k r mrmr crcr mrmr crcr mrmr crcr -1/k s 1/k s -1/k s 1/k s 1/k b -1/k b CoCo CoCo 1:  e  e :1 1:  c  c :1 1:  b  b :1 /4  /4 Input Output vivi RQRQ RQRQ vovo VPVP Bridging Beam Coupling Beam Resonator  vovo vivi

22. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06  vovo vivi Micromechanical Filter Circuit 1/k r mrmr crcr mrmr crcr mrmr crcr -1/k s 1/k s -1/k s 1/k s 1/k b -1/k b CoCo CoCo 1:  e  e :1 1:  c  c :1 1:  b  b :1 /4  /4 Input Output vivi RQRQ RQRQ vovo VPVP Bridging Beam Coupling Beam Resonator All circuit element values determined by CAD layout Amenable to automated circuit generation

23. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Frequency [MHz] Transmission [dB] P in =-20dBm In Out VPVP Sharper roll-off Loss Pole Performance: f o =9MHz, BW=20kHz, PBW=0.2% I.L.=2.79dB, Stop. Rej.=51dB 20dB S.F.=1.95, 40dB S.F.=6.45 Performance: f o =9MHz, BW=20kHz, PBW=0.2% I.L.=2.79dB, Stop. Rej.=51dB 20dB S.F.=1.95, 40dB S.F.=6.45 Design: L r =40  m W r =6.5  m h r =2  m L c =3.5  m L b =1.6  m V P =10.47V P=-5dBm R Qi =R Qo =12k  [S.-S. Li, Nguyen, FCS’05] 3CC 3 /4 Bridged  Mechanical Filter [Li, et al., UFFCS’04]

24. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Square-Plate Micromechanical Resonator Coupling Beam h WsWs gap, d o LrLr 50  -Terminated 68-MHz Coupled- Array  Mechanical Filter Use square-plate  mechanical resonator arrays Lower end resonator impedance & raise power handling 50  termination w/ L-network L r = 16  m h = 2.2  m d o = 90nm L r = 16  m h = 2.2  m d o = 90nm R Q = 12k  R term = 50  R Q = 12k  R term = 50  f o =68MHz BW=190kHz P BW =0.28% I.L.<2.7dB f o =68MHz BW=190kHz P BW =0.28% I.L.<2.7dB [Demirci, Nguyen 2005]

25. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 RF Channel-Selection

26. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for High Q Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 Wireless Phone Received Power Frequency  RF Desired Signal

27. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for High Q Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 Wireless Phone Received Power Frequency  RF Desired Signal

28. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for Q’s > 10,000 Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 Wireless Phone Received Power Frequency  RF Desired Signal If can have resonator Q’s > 10,000

29. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for Q’s > 10,000 Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 Wireless Phone Received Power Frequency  RF Desired Signal If can have resonator Q’s > 10,000

30. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for Q’s > 10,000 Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 If can have resonator Q’s > 10,000 Wireless Phone Non-Coherent FSK Detector? (Simple, Low Frequency, Low Power) Front-End RF Channel Selection Received Power Frequency  RF Desired Signal Substantial Savings in Cost and Battery Power

31. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Motivation: Need for Q’s > 10,000 Antenna Demodulation Electronics The higher the Q of the Pre- Select Filter  the simpler the demodulation electronics Pre-Select Filter in the GHz Range Presently use resonators with Q’s ~ 400 If can have resonator Q’s > 10,000 Wireless Phone Direct-Sampling A/D Converter  Software-Defined Radio Maximum Flexibility  one circuit satisfies all comm. standards Front-End RF Channel Selection Received Power Frequency  RF Desired Signal

32. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 RF Channel-Select Filter Bank Bank of UHF  mechanical filters Switch filters on/off via application and removal of dc-bias V P, controlled by a decoder Transmission Freq. Transmission Freq. Transmission Freq. 12n34567 RF Channels Remove all interferers!

33. C. T.-C. Nguyen, “Towards MEMS-Based Receivers,” BWRC Winter Retreat, 1/(8-9)/06 Conclusions Vibrating RF MEMS have achieved Vibrating RF MEMS have achieved  Q’s >10,000 at GHz frequencies in sizes less than 20  m in diameter and w/o the need for vacuum encapsulation  TC f ’s < -0.24 ppm/ o C (better than quartz)  aging at least on par with quartz  circuit-amenable characteristics  VLSI potential Probable evolution of products based on vibrating RF MEMS: Probable evolution of products based on vibrating RF MEMS:  timing devices using micromechanical resonators  communication-grade frequency synthesizers  single-chip of all needed high-Q passives  mechanical radio front-ends … In Research: Time to turn our focus towards mechanical circuit design and mechanical integration In Research: Time to turn our focus towards mechanical circuit design and mechanical integration  maximize, rather than minimize, use of high-Q components  e.g., RF channelizer  paradigm-shift in wireless design  even deeper  frequency computation What’s possible with an unlimited supply of high-Q passives? What’s possible with an unlimited supply of high-Q passives?